No spark/ballast resitor/ coil on 65 D100, need advice.

[Steve]

Hi- I have some electronics and electrical experience but next to no automotive troubleshooting experience. So I'm a bit green and could use some help.

I've just started bringing my Grandpa's (now mine) '65 series one D100 back to life after it sat for about 17yrs. I've got no spark at the plug when grounded. -Batt is good, ballast resistor shows continuity (about 4 ohms) and the starter turns over very well. The positive supply to the coil from the ballast resistor shows 13vlts at key on and drops to 10.5 or so when cranking. It's the poly 318. Is that what I should be seeing at that wire? I don't have a spark arrestor so i haven't tested the coil directly yet, and i haven't done the gap the secondary wire and see if it fires test either. the plate under the points has a solid ground, and both condensers are not shorted to themselves and have continuity from case to ground.

Can anyone give me some advice on how to further troubleshoot the system? OR...is a problem obvious to someone else already?

Any help would be appreciated.

Thanks, Steve

[WD]

Have you checked the points yet? They should open and cause a spark as the dizzy rotates. If they aren't opening and closing properly (whether or not they spark is a different matter) all other testing is basically useless.

[Steve]

Thanks for your reply, the points are opening and closing about .016. The plate under the point also has a solid ground. I'm going to fender test the coil, does anyone know what value the ballast resistor on a 65 D100 should be (poly 318)?

Thanks ,Steve

[712edf]

I don't think its your ballast, since that gets bypassed while cranking and you say your getting full voltage at coil. The full voltage at coil is cranking only, should be 5-6V while running.

Coil or distributor. I'd start with coil.

Bucky

[Roxyflash]

Heres a simple test take a jumper wire from battery positive to the the postive of coil it should run.This will eliminate all the switch wiring ballast relay and so forth.If it runs then your problem is the wiring probably the plug in harness at fire wall.If it dont run its either the coil or distributor unless it jumped the timing.

[Steve]

So let me get this straight cause I've now heard three versions of how the ballast resistor is supposed to work. I was first told that at key on ( not running) I should see 4-6vlts at the +v for the coil, and then due to the bypass from the ignition switch, full batt voltage (or so ) while cranking, minus the induced load of the starter pulling on the batt. I have to say though after some thought, your version makes more sense to me. The wire from the ignition switch is connected to the hot wire for the coil, so at key on the coil ought to have full bat voltage. when cranking it drops to 10.5 and that makes sense for the extra load. When running the other side of the ballast resistor comes off of the back of the regulator which would be adjusting field when the alternator is running...right? Do i have it yet? Just for the record, my bet is also on the coil and maybe the secondary wire to the distributor, etc Appreciate you helpin' a newbie troubleshooter. Hey how do you guys get pics of your truck up here with our posts?

Thanks, Steve

[Steve]

Heres a simple test take a jumper wire from battery positive to the the postive of coil it should run.This will eliminate all the switch wiring ballast relay and so forth.If it runs then your problem is the wiring probably the plug in harness at fire wall.If it dont run its either the coil or distributor unless it jumped the timing.

Got some advice and thought I'd try a version of your suggestion. I'll pull the coil out of the whole system, get it +V from the batt to the positive post, attach a wire to the negative post and ground it. Park a spark arrestor in the secondary and ground it so i can see it, and then lift the ground on the neg post of the coil. That should make it fire right? Just like the points opening, right?

[dodgeboykim]

You can do the same thing by doing the hot wire trick and just opening and closing the points manually with a screwdriver.

[Roxyflash]

Take and do the jumper wire test just pull one plug wire off and plug see if it sparks.This way you know the plug is sparking when its suppose to.The ballast resistor is there to keep your points from frying.With just ignition on the power goes tru the resistor dropping voltage.When cranking the start wire jumps to the side of resistor to get full voltage to the ignition.After it starts its goes tru the resistor to drop the voltage.This has nothing to do with the voltage regulator.

[EGroscup]

With it sitting that long the points have oxidized and are not passing current from the coil. Take the points out and file or sand them until they are clean. Reinstall, regap and you should have spark. E.

[Steve]

Certainly couldn't hurt to dress up the contacts, so I'll do that. I checked with a meter to see if they were opening and there was no continuity across the points, but I didn't think to do the test the other way...? -good lesson for me, once again, never assume! It's funny, I'm a sound man and I know all this stuff when I'm trouble shooting a sound system, but when you're learning something new, basic concepts can just go right over your head! For seven bucks I went ahead and bought a new ballast resistor. -also a new set of good quality wires. Thanks for the screwdriver points trick, didn't know about that one, as this is my first foray into troubleshooting coil and points etc.. I'll let you know how it goes now that I'm confident things are connected.

Thanks guys.

[Steve]

The coil failed the hot-wire test, so there's a new one installed. I haven't cleaned the points yet, but I've got another question; With a new ballast resistor, I'm seeing 13v at the batt. posts and 12v at the coil positive supply at key on position. Seems to me that dropping to 12v isn't much help to the coil. If 4-6v is what I should be seeing, what do you think is going on? The wiring is clearly original in the engine compartment and appears to be the same under the dash.

Think I'll isolate the resistor itself and see if it's actually providing any resistance. One of you guys wouldn't happen to know off-hand what the value of that resistor should be do you? (not on the package) If i just supply it with 12v (13) off the pos. post, shouldn't I see voltage drop at it's rear end? what kind of drop would you expect?

Thanks

[Sterno]

I've got another question; With a new ballast resistor, I'm seeing 13v at the batt. posts and 12v at the coil positive supply at key on position. Seems to me that dropping to 12v isn't much help to the coil. If 4-6v is what I should be seeing, what do you think is going on?

Thanks

Remember, If your points are open your circuit is incomplete and therefore both sides of the Ballast resistor will show 12V. short the negative of the coil to engine ground (or short the points) while measuring the positve coil terminal voltage, I bet it'll drop to 6-8 volts.

[Steve]

I've got another question; With a new ballast resistor, I'm seeing 13v at the batt. posts and 12v at the coil positive supply at key on position. Seems to me that dropping to 12v isn't much help to the coil. If 4-6v is what I should be seeing, what do you think is going on?

Thanks

Remember, If your points are open your circuit is incomplete and therefore both sides of the Ballast resistor will show 12V. short the negative of the coil to engine ground (or short the points) while measuring the positve coil terminal voltage, I bet it'll drop to 6-8 volts.

Oh. I hadn't thought of it that way. I still don't quite understand (i don't have an accurate wiring diagram). If you don't mind, I'll write out how I've been thinking the circuit works and please correct or educate me where needed. (over simplified) 12v supply from the battery to ignition switch. At key on 12v to bottom (say pin 1)of ballast resistor, through the resistor to positive primary of the coil. A wire to pin 2 of the resistor acts to bypass the resistor from the cranking position on the switch to supply full voltage to the coil. OK so far? This is the primary of the coil. The points are breaking the ground path from the negative on the coil when their open, right? When closed for dwell the primary circuit flows current to ground building the charge in the secondary. When the points open the charge in the secondary seeks ground through the rotor to the plug / block. How am I doing? ...I think I get it. When the points are open it's just floating voltage, because there no path to ground on the back side of the resistor, there's no load for voltage drop. Is that right? (Sounded decent)

Thanks so much,

Steve

[JimE]

Early 4 headlight 65: http://www.sweptline.com/tech/62_65wire.jpg
later 65 with 2 headlights: http://www.sweptline.com/tech/65wire.jpg
Jim

[Roxyflash]

http://autorepair.about.com/cs/generali ... 52502a.htm

[EGroscup]

You have it right Steve, the current flows through the primary winding of the coil through the points creating a magnetic field in the coil. When the points open, current stops flowing causing the magnetic field to collapse and that induces the high voltage in the secondary coil winding to be sent on its way to the appropriate spark plug. File those points clean and fire it up.

[Steve]

You have it right Steve, the current flows through the primary winding of the coil through the points creating a magnetic field in the coil. When the points open, current stops flowing causing the magnetic field to collapse and that induces the high voltage in the secondary coil winding to be sent on its way to the appropriate spark plug. File those points clean and fire it up.

Thanks for your advice. It was the key concept that I hadn't quite wrapped my head around yet. I bought new points , cap, rotor and condenser, but haven't installed yet. I cleaned up the old points, but they were still a bit intermittent, though, as advertised, 6-8 volts when conducting. I'll take out the set that's in there an clean up really well to have for a spare. Should have spark soon....then the carb, the fuel pump and the tanks.

Thanks, guys.

Steve